Mercury vapor has been removed from gas streams by a number of different adsorbents. See for example, U.S. Pat. No. 3,194,629 describing activated carbon impregnated with potassium triiodine or sulfur; U.S. Pat. No. 3,876,393 describing activated carbon impregnated with sulfuric acid; U.S. Pat. No. 3,193,987 describing activated carbon impregnated with silver or copper salts; and U.S. Pat. No. 4,101,631 describing zeolites containing elemental sulfur. Generally, these adsorbents are only effective when relatively large concentrations of mercury are present and, each adsorbent has a lower limit, below which, mercury vapor is either inefficiently adsorbed or not adsorbed at all.
It has been discovered that carbon molecular sieves impregnated with a mercury reactive material are effective adsorbents especially of very low concentrations of mercury vapor. It was also found that carbon molecular sieves impregnated with sulfur are less adversely affected by water and temperature than the prior art adsorbents.